The present invention relates to a filling element for filling machines, especially for single and multi-chamber counter pressure filling machines, with the filling element including liquid introduction means which leads to the interior of a container, for example a bottle, which is pressed onto the filling element so that it can be filled; the liquid introduction means, for example a filling tube, has at least one liquid flow valve, which is under the influence of an opening spring and of an electrically controlled valve actuating device which acts counter to the opening spring; also provided is at least one gas-conveying system having at least one electrically controllable shutoff valve; such a gas-conveying system might be a return gas withdrawal system which leads from within the container which is to be filled, and which has as least one return gas flow restrictor and, associated with each of the latter, a connecting passage, at least one of which includes one of the electrically controllable shutoff valves for periodically opening and closing off the associated connection passage.
A filling element of this general type is disclosed in U.S. Pat. No. 4,369,820, issued on Jan. 25, 1983 to the Assignee of the present application. With this heretofore known filling element, the actuating device for the shutoff valve for the connecting passage of the return gas flow restrictor is an electromagnet attached directly to the lower portion of the filling element. The valve actuating device of the liquid flow valve is also formed essentially by an electromagnet which is placed upon the upper portion of the filling element. These heretofore known filling elements are deficient, especially because the shutoff valve actuating device, which contains an electromagnet as the essential actuating element, is exposed to a large extent to liquid entry from the outside due to the manner in which it is attached to the filling element, and due to its location thereon. This efficiency exists not only during cleaning of the filling element, but also to a greater or lesser extent during the overall operation, and especially when after a bottle has broken, the filling element, especially the lower portion thereof, must be intensively sprayed with cleaning fluid to remove glass splinters. Due to these conditions and necessities, it is unavoidable that after a period of time moisture enters openings provided in the housing for the supply of power and for movable parts, especially since the cleaning fluid, which is combined with wetting agents, is able after a period of time to penetrate even the most careful seals. moisture which penetrates into the interior of the electromagnets adversely affects the electrical insulation, and can therefore cause current leakage which is particularly disruptive if the electromagnet is connected to an electronic switching arrangement which controls the filling element. Furthermore, moisture which penetrates the housing of this actuating device adversely affects the ease of motion of the magnet armature.
German Offenlegungsschrift No. 20 45 238 disclosed counter pressure container and bottle filling machine having pneumatically controlled filling elements, according to which the liquid flow valve has a pneumatic control element which closes under spring pressure and is controlled by a switchable, spring-loaded two-way valve, while the line which spans the return gas flow restrictor is controlled by a pneumatically operated control valve.
However, these heretofore known filling elements with pneumatic control and pneumatic valve actuation have the deficiency that electrical probes which respond precisely and reliably to a predetermined filling height are not provided, so that no precise and uniform filling height can be achieved with such known pneumatically controlled filling elements, as is the case with electrically controlled filling elements.
It is an object of the present invention, while maintaining the high precision and uniformity of the filling height which are possible with electrical control, to improve an electrically controlled filling element for filling machines so that disruptions in operation no longer occur due to the entry of liquid into the respective actuating devices of the valves, especially into the actuating device of the shutoff valve disposed in the connecting passage for the return gas flow restrictor.